Conventionally, printing sheets for heat transfer have been known each of which comprises a film substrate, an adhesive layer provided on one surface thereof and a separator covering the adhesive layer and is wound to form a wound product. However, such sheets have the problems that the separators become unnecessary articles such as wastes when heat transfer patterns are imparted to the printing sheets to put the sheets into practical use as labels, and that the separators are flexible and difficult to be released because they are formed of thin films.
In the above, if the printing sheets have no separators covering the adhesive layers, it becomes difficult to rewind the wound products, and the sheets adhere to a progressive mechanism in a heat transfer printer, which results in the difficulty of practical use as the printing sheets. When release coats are provided on surfaces of the film substrate in accordance with the adhesive sheets having no separators, the fixing of ink on the film substrates becomes difficult, resulting in the failure of practical use as the printing sheets.